KENWOOD L-02A

Commentary

This pre-main amplifier is equipped with a unique dynamic linear drive circuit developed by combining the two speaker drive theories which Trio is proud of.

It is equipped with a dynamic linear drive circuit that combines a dynamic power supply that provides a stable output even under low impedance loads and a Σ drive theory that guarantees performance at the input terminal of the speaker with excellent speaker control ability.
The Dynamic Linear Drive Circuit consists of two amplifiers at the output, a low-power amplifier and a high-power amplifier. Most of the signal is processed by a high-quality low-level amplifier with a low distortion factor. This low-level amplifier can handle up to approximately 50W. It is driven by a huge power supply that can output 170W, so it has excellent characteristics that are not affected by the load fluctuation of the speaker. In addition, the high-power amplifier operates only for a very short period of time when the peak signal passes while maintaining low distortion, so there is little heat generation and almost no internal loss.
As a result, we have achieved high sound quality from small output to large output without sacrificing the quality of small to medium output, which has been a problem with high power amplifiers.
In addition, the TRIO's unique Σ drive system minimizes distortion during mounting of the speaker and realizes a high damping factor at the end of the speaker cable.

The equalizer amplifier section is equipped with a unique dual-head equalizer amplifier that completely replaces the differential circuit and NF element of the input section for MC and MM cartridges.
For MC cartridges with low impedance, an input circuit using a cascode load with 4 parallel bipolar transistors is used. For MM cartridges with relatively high impedance, an input circuit using a cascode load with Hi-gmFET is used.
As a result, it is possible to select an input element that matches the characteristics of the cartridge. In addition, it is possible to obtain the same effect as the MM/MC dedicated equalizers. It is possible to achieve a low distortion factor by applying almost the same amount of negative feedback. It is possible to concentrate the two circuits of the dedicated equalizer amplifier into one circuit, and it is possible to thoroughly pursue the circuit performance.
The basic amplifier section employs a 3-stage differential-amplifier circuit with various low-current circuits and improved characteristics such as CMRR and SVRR by improving the stability of each bias voltage. The final stage is a 2-stage Darlington complimentary service output-circuit with a Hi-ft power amplifier transistor. Both the A-class and B-class stages are equipped with independent rectifier circuits. As a dedicated power supply for the equalizer, the A-class and B-class stages are equipped with independent rectifier circuits to prevent adverse effects of current changes in the output-circuit from reaching the first stage.

The Σ drive system was developed for the purpose of driving the speaker with a signal similar to the input waveform of the amplifier.
As a result, even if a connection cable of several meters is used, waveform deformation does not occur at the speaker input terminal, and speaker drive with faithful waveform is realized.

A dynamic power supply is used to provide excellent drive performance even for low impedance loads.
In the L-02A, a dynamic power supply using a large-capacity Chemicon with one channel of 36,000 μ F and a huge power transformer does not operate the current limiter even with 2 Ω load, improving the speaker drive performance.

The power supply section of the power amplifier uses a two power supply system on the right and left sides. A high-capacity Chemicon and a large VA transformer are used for each channel. This reduces dynamic crosstalk (leakage between the left and right channels through the power supply section) and maintains high power even when driven with low impedance.
In addition, the voltage amplifier stage is an independent power source with dedicated windings to eliminate the influence of the power amplifier stage, and the first stage differential amplifier circuit with a small signal level is equipped with a decoupling circuit using constant current + constant voltage elements to eliminate interference in the voltage amplifier circuit.

The power amplifier circuit consists of a differential amplifier circuit using one chip dual FET for the first stage and a dual FET with excellent harmonic characteristics for the second stage to prevent unnecessary phase rotation in a high high-frequency band and to expand the frequency characteristics in open loop to suppress switching distortion and crossover distortion. The output stage is a parallel push-pull DC amplifier.

Each stage is arranged along the signal flow to prevent electrostatic or electromagnetic return from the second stage to the first stage, and each stage is completely shielded to eliminate return.
Furthermore, the power transformer is isolated by installing it in a separate case.

The power transistor is attached to a large radiator, and the frame and chassis that support the radiator are 1.6 times thicker than normal, making the structure resistant to vibration.
In addition, the front panel is a double panel of 4 mm and 6 mm, and the case is made of 4 mm thick aluminum to prevent howling.

For each of the 4 transformers and 8 power supplies, the structure of the transformer, condition of the winding, mounting of the chassis, connection, etc. are all designed according to the Σ drive theory, so that no potential difference is generated between each earth.
In particular, even for patterns and wiring on printed circuit boards, a single ground reference point is defined so that each ground does not have a common impedance.

The power transformer is a separate power supply using an easy docking method that does not require complicated connector wiring.
When the depth of the shelf to be set is insufficient, it can be separated with the attached one touch connector cable.

The less frequently used control knobs are stored in the slide-type electric control box.
This control box is driven by an ultra-low noise, low-speed, high-torque DC coreless motor, and can be opened and closed smoothly with one touch.
If you bump into something or pinch your finger during operation, the operation is reversed to prevent self-occurrence.
In addition, if the power switch is turned off with the control box extended, the power is automatically turned off after the box is retracted.

Model Rating

Type	DLD Circuit Integrated Amplifier
Rated Output (Both Channel Operation)	170W + 170W (8 Ω, 20 Hz to 20 kHz) 250W + 250W (4 ω, 1 khz, 0.003% THD)
Dynamic Power	390W + 390W (4 Ω) 250W + 250W (8 Ω)
Total harmonic distortion rate (20 Hz to 20 kHz)	Tuner, Aux, Tape-to-SP jacks : 0.003% (8 Ω at rated output) 0.003% (8 Ω at 1/2 rated output) Phono → SP terminal (Vol-20dB) : 0.004% (at rated output)
Intermodulation distortion factor (60 hz : 7 khz = 4 : 1)	Tuner, Aux, Tape → SP terminal : 0.003% (8 Ω)
Frequency characteristic	DC ~ 400 kHz -3dB (Tuner, Aux, Tape → SP terminal)
SN ratio (IHF-A, at rated output, SP terminal)	Phono MM : 91 dB or more Phono MC : 73 dB or more Tuner, Aux, Tpae : 110 dB or more
Subsonic filter	18 Hz, 6dB/oct.
Loudness control (Volume-30dB)	30 Hz to 100 Hz Continuously Variable +3dB/+6dB/+9dB
Damping factor (55 Hz, 8 Ω)	10,000 or more
Rise time	0.9 μ s
Slew rate	± 150 V / μ s
Input Sensitivity / Impedance (at rated output, SP terminal)	Phono MM : 2.5mV/47k Ω Phono MC : 0.1mV/100 Ω Tuner, Aux, Tape : 150mV/30k Ω
Phono maximum allowable input (1 kHz, 0.0007% distortion factor)	MM:350mV MC:15mV
Phono RIAA deviation	20 Hz to 20 kHz ± 0.2 dB
Output Level / Impedance	Tape rec (pin) : 150mV/430 Ω Pre out (maximum output) : 2V/600 Ω
Power supply voltage	100 VAC, 50Hz/60Hz
Rated power consumption (Electrical Appliance and Material Control Law)	420W
Power outlet	Power switch interlock : 2 systems, 250W Power switch not linked : 1 system, 500W
External dimensions	Body : Width 480x Height 183x Depth 343 mm Power Supply : W 480x H 181x D 163 mm Docked : W 480x H 183x D 482 mm
Weight	Body : 17.5 kg Power Supply : 17 kg Docked : 34.5 kg